DE4214621C1 - - Google Patents

Description

The invention relates to a camouflage device for Thermal imaging devices in the preamble of claim 1 Art.

In thermal imaging devices, it is emitted from all objects sent temperature-dependent heat radiation - light in infra red spectral range - for mapping the landscape restricted visibility due to e.g. B. haze or Darkness used.

The infrared radiation is viewed through optics scene on a detector, which usually consists of a There is a multitude of elements, shown.

With the common technical solutions arise in the Detector elements correspond to the heat radiation received de electrical current or voltage changes.

These electrical signals are amplified and be known technology made visible for viewing.

The basics and embodiments of this technique are described in "In infrared technology basics, radiation transmitters and detectors Infrared Imaging and Playback Telemetry "from K. Stahl and G. Miosga, 2nd edition, Heidelberg; Hüthig, 986.  

Thermal imaging devices are becoming almost because of their high cost used exclusively in national defense; she he possible attackers, especially tanks, at night watch and, if necessary, fight, taking out the tank cover itself if possible through deepening of the terrain or Plant growth lasts. Step in the observed landscape Vehicles because of their own heat much more clearly than when observed with conventional optical viewing means, which is why thermal imaging devices are also used for daytime observations be set.

Most detector materials require that the detector is cooled to a low temperature (e.g. 80 K), d. H. to a temperature that is approx. 200 K below the temperature, which averaged from the heat radiating environment of the thermal imaging device results.

This large temperature difference causes the disadvantage that an opposing observer, who in turn is with a Thermal imaging device is equipped and another thermal imaging be seeks, the light entry opening as a striking stain perceives in the scene.

In particular, this disadvantage affects when the observing devices are of the type in which the detector consists of fewer elements than correspond to the image field and the picture only by swiveling the received heat beam by means of a beam deflecting means via this detector individual elements are created (scanning thermal imaging device).

In this case, the spot usually flashes because of the existing different deflection frequencies of the beam-Ab steering means that take turns looking at the "cold" Periodically release the detector and the warmer inside of the device.  

Because the eye is very sensitive to such periodic changes perceives, the thermal imaging device, and thus that too belonging military object, despite camouflage according to the state of the Technology, discovered quickly.

The invention has for its object a camouflage device device for thermal imaging equipment that prevents it mutually observing thermal imagers, because of their entrance pupils contrasting with the scene being viewed discover.

The solution succeeds with the measure specified in claim 1 took.

Since the contrast difference between entrance pupil and heat environment due to the radiation deficit of the Detek the radiation level of the environment arises, the invention provides such radiation as a supplement add to the outgoing from the detector that the Sum of the radiation leaving the entrance pupil that of corresponds to the radiation caused by the environment.

For this purpose there is an additional defined radiant Radiation source provided, the radiation of which Radiation combiner with the radiation emitted by the detector is united.

A halogen lamp is an economical solution beaten, the glowing filament of which in most cases required temperature of 3000 K.

Of course, other heat sources are also ge suitable if they are able to meet the required dif to emit reference radiation.  

For a more precise approximation that left the entrance pupil send total radiation to the ambient radiation, it is possible Lich, the power of the radiation source depends on that of ambient temperature determined by a temperature sensor To control current or aperture variation or, at higher An say, additionally by means of a front of the lens brought radiation meter, compared to the environment regulate radiation precisely.

The radiation from the radiation source is on the angular range to limit the detector radiation.

For thermal imaging devices of the scanning type is also Radiation from the radiation source is in the same direction as the image to move the detector.

Because the union of detector and radiation source beam tion inside the thermal imager can be very expensive can or with devices already in use Retrofitting in the device beam path is virtually impossible there is the possibility of mixing the radiation via the external cover window of the thermal imager. In the case of scanning thermal imaging devices, there is a radiation deflection tel in the external beam path, which is synchronous and the movements of the inner radiation deflection are effective means with.

For scanning devices it is with low demands on the Camouflage acceptable to deflect the radiation waive if the additional radiation on such Brightness value is raised that the total brightness by the mean of the ambient radiation both after dark as pulsates towards bright. The resulting blinking effect on one clearing thermal imaging device monitor is then clearly ge wrestler than a stain that depends on the ambient brightness "dark" flashes.

An embodiment of the invention is shown in the drawing and is described in more detail below.

Show it

Fig. 1 illustrates the basic principle of a thermal imaging device with an areal detector array;

Figure 2 is a simplified representation of a thermal imaging device with a single column detector arrangement and beam deflection means (scanner).

3 extending in a thermal imaging device having a linear Anord resultant visual field voltage of detector elements with the pivoting therein detector image.

Fig. 4 shows the beam path of a thermal imaging device with a linear detector structure and deflection device in which the radiation of a radiation source is mixed with the aid of a beam combiner.

The basic principle of a thermal imaging device shown in FIG. 1 shows how the object 1 is imaged with the objective 2 on a detector 3 , the individual elements of which are arranged flat.

As a rule, the elements of the detector 3 convert the infrared radiation of the object 1 projected onto them into equivalent voltages, which are amplified by an amplifier 4 and made visible on a monitor 5 .

In Fig. 2, the structure of a thermal imaging device is shown, in which the detector 3 consists of only a single row of detector elements.

In this embodiment, it is necessary to pivot the image of the object 1 imaged by the objective 2 over the detector 3 . Each individual element of the detector 3 then has an image line on the monitor.

To pivot about the imaged picture from the lens 2 on the detector 3 is tor in the beam path of the device prior to Detek 3, a beam deflection means (scanner) is installed. 6

Fig. 3 shows the arrangement at a scanning field of view 9 de arise with the detector located therein Figure 8.

Because of the necessary cooling of the detector 3 , the detector image 8 pivoted through the field of view 9 is in strong contrast to the rest of the field of view 9 .

In Fig. 4 the arrangement is shown in which, according to the invention, the radiation of an additional radiation source 11 in the form of a light bulb, the radiation surface of which is projected via a beam combiner 10 for imaging in the object plane into the lens 2 of the thermal imaging device 7 .

The beam combiner 10 is inserted as a partially transparent mirror obliquely to the optical axis of the thermal imaging device beam path between objective 2 and detector 3 . Its division ratio is chosen so that the thermal radiation of the object is only slightly weakened, for. B. 10%.

The radiation emitted by the detector 3 is imaged by him in the same way as the radiation from the radiation source 11 via the objective 2 in the object plane.

A viewer of the lens entrance pupil sees that Combination of both radiations.  

In a scanning thermal imaging device 7 is included in addition to the above-mentioned functional elements have the previously mentioned beam deflector. 6

The installation location of the radiation source is chosen so that the Detector radiation and the radiation from the radiation source be steered in the same direction at the same time.

Reference list

1object
2ndlens
3rddetector
4 amplifiers
5monitor
6Radiation deflector
7Thermal imager
8thDetector image
9Field of view
10thRadiation unifier
11Radiation source

Claims (7)

1. camouflage device to reduce the detectability of a thermal imaging device with a cooled detector, characterized in that to the emerging from the entrance pupil of the thermal imaging device, compared to the environment lower radiation intensity by a radiation source, such a radiation intensity is added that for observing the thermal imaging device the entrance pupil of the former Thermal imaging device with the radiance of the surroundings shines. 2. Device according to claim 1, characterized, that the radiation source regulate in the radiance is incandescent glow body, the radiation of which ab visual optics using a beam combiner in the beam path of the thermal imager is inserted.   3. Device according to claim 1 and 2, characterized, that the ray combiner as a partially permeable Spie gel is executed, which is in the beam path of the heat is located. 4. Device according to claims 1 to 3, characterized, that the ray combiner in the ray path of the heat image device between a radiation deflecting means and Detector is arranged so that from the rays source inserted radiation from the radiation deflecting means is steered in the same direction as that radiation emanating from the detector. 5. Device according to claims 1 to 4, characterized, that it has a control device that is dependent from an outside of the thermal imager Temperature or heat radiation sensor the radiation regulates the strength of the "camouflage" radiation source in such a way that the sum of both radiations when leaving the Thermal imaging device corresponds to the radiation of the environment.   6. The device according to claim 1, characterized, that the difference radiation, not directly that from the Thermal imaging device is mixed with emerging radiation, but separately axially parallel or concentric to Thermal imager lens close to its optical axis is sent out. 7. The device according to claim 6, characterized, that the radiation emitted by a radiation-Ab steering means is steered synchronously in the direction in which directs the radiation from the thermal imager detector becomes.